The invention relates generally to welders, and more particularly to a welder configured to perform a welding operation in which a pulsed waveform is applied to welding wire as the wire is advanced from a welding torch.
A wide range of welding systems and welding control regimes have been implemented for various purposes. In continuous welding operations, metal inert gas (MIG) techniques allow for formation of a continuing weld bead by feeding welding wire shielded by inert gas from a welding torch. Electrical power is applied to the welding wire and a circuit is completed through the workpiece to sustain an arc that melts the wire and the workpiece to form the desired weld.
Advanced forms of MIG welding are based upon generation of pulsed power in the welding power supply. That is, various pulsed regimes may be carried out in which current and/or voltage pulses are commanded by the power supply control circuitry to regulate the formation and deposition of metal droplets from the welding wire, to sustain a desired heating and cooling profile of the weld pool, to control shorting between the wire and the weld pool, and so forth.
While very effective in many applications, such pulsed regimes render control of wire feed rates difficult. In certain known techniques, for example, attempts are made to control wire feed speed based upon the frequency of the pulsed waveforms. This may require rapid changes in wire feed speed, however, rendering control difficult. These difficulties are exacerbated when certain types of wire are used, such as aluminum and its alloys. Because aluminum welding wires cannot support high column loads as can steels, a motor designed to push the wire from a wire feeder through the welding torch is most often supplemented by a motor disposed in the torch to pull the wire. Coordination of both of these motors may then be required, and these again based upon the pulse frequency. Such coordination is difficult and often leads to less than optimal system performance.
There is a need, therefore, for improved welding strategies that allow for welding in pulsed waveform regimes while improving wire feed control.